If you have a slim, your options are limited to E3 (as stated, known to suck moose-balls) or Teensy++ 2.0 (requires soldering). In my opinion, neither is worth the risk if you can't solder, so if you want backups, you should start practicing.
I know the Progskeet states that it works with NOR, but last time I had looked into it, it had only worked on NAND consoles. That was a while back however, and I ended up just getting a Teensy++ 2.0 myself. Maybe someone who's looked into the software they run more recently than I can give you more info on that. Either way, I wish you luck.
Edit: Progskeet does work with NOR, so I'd say go for that one. =D
Edit2: Uploaded the pinout diagrams from Progskeet.com
Edit3: Once you get the flasher installed, here's a tutorial on how to use 'em